Archive files with multiple passwords

How to create archives
with multiple passwords

Mainstream archive formats standards (including 7Z, RAR, and ZIP/ZIPX)
provides file-level encryption scheme.
That architecture choice means a single archive can contain files
encrypted with different passwords - ideally a different password for
each file.
Also, this allows a single archive to contain both encrypted and non
encrypted content.

Updating existing
archives let user
provide (or omit) an arbitrary password at each instance, allowing to
(potentially) protect each group of files with a different password.

PEA format supports only archive-level encryption so allows / guarantee
a
single password being used - which may be an advantage or disadvantage
depending on the user's needs.

How to extract archives
with multiple passwords

Extracting data from encrypted archives requires the correct password
being provided to the decryption procedure, otherwise protected data
will result unreadable and extraction procedure will fail.

Consequently,
when working with archives whose content is selectively protected by
different passwords for different
groups of files, it is needed to extract each group of archived file
with its own password, in separate passes.

An different case of multi-password archive is when one or more
existing password-protected archives are added to a new password
protected archive container, and (potentially) so on, so at each
iteration a
different password is added.This may be preformed in
order to have different passwords and/or
different types of cryptography to
be applied to protect the content at each layer, but comes at cost of
requiring
multiple archiving iterations to build such archive - and obviously to
equally require multiple extraction iterations, until the actual
plain-text
content is reached.
Since iterations will happen sequentially, there is no technical
difficulty for any archiving utility to handle this case of double ot
triple or multiple password layers, providing
appropriate
password at each serial archiving/extraction iteration step.